This invention generally relates to the art of electrical connectors and, particularly, to a system for terminating the metallic shield of a high speed cable, such as the metallic braid of the cable.
A typical high speed cable includes a center conductor or core surrounded by a tube-like inner dielectric. A shield is disposed outside the inner dielectric for shielding and/or grounding the cable. The shield typically is a tubular metallic braid. However, one or more longitudinal conductive wires have also been used and are commonly called xe2x80x9cdrain wires.xe2x80x9d An insulating jacket surrounds the composite cable outside the shield.
Various types of connectors are used to terminate high speed cables. The connectors typically have contacts which are terminated to the center conductor or core of the cable. The connectors also have one form or another of a terminating member for terminating the metallic shield of the high speed cable, usually for grounding purposes. A typical system in such connectors terminates the metallic shield to the terminating member by soldering. Other systems use crimping procedures to crimp at least a portion of the terminating member securely to the metallic braid for commoning purposes.
With the ever-increasing miniaturization of the electronics in various industries, such as in the computer and telecommunications industries, along with the accompanying miniaturization of electrical connectors, considerable problems have been encountered in terminating miniature high speed cables, particularly in terminating the metallic shield of the cable. For instance, the outside diameter of a small coaxial cable may be on the order of 0.090 inch. The outside diameter of the inner dielectric surrounding the conductor/core may be on the order of 0.051 inch, and the diameter of the center conductor/core may be on the order 0.012 inch. Coaxial cables having even smaller dimensional parameters have been used.
The problems in terminating such very small coaxial cables often revolve around terminating the metallic shield of the cable. For instance, if soldering methods are used, applying heat (necessary for soldering) in direct proximity to the metallic shield can cause heat damage to the underlying inner dielectric and, in fact, substantially disintegrate or degrade the inner dielectric. If conventional crimp-type terminations are used, typical crimping forces often will crush or deform the inner dielectric surrounding the center conductor/core of the cable.
The above problems are further complicated when the metallic shield of the high speed cable is not terminated to a cylindrical terminating member, but the shield is terminated to a flat terminating member or contact. For instance, it is known to terminate the tubular metallic shield or braid of a coaxial cable to a flat ground circuit pad on a printed circuit board. This is accomplished most often by simply gathering the tubular metallic braid of the coaxial cable into a twisted strand or xe2x80x9cpigtailxe2x80x9d which, in turn, is soldered to the flat ground pad on the circuit board.
Another example of terminating the metallic shield or braid of a coaxial cable to a flat ground member is shown in U.S. Pat. No. 5,304,069, dated Apr. 19, 1994 and assigned to the assignee of the present invention. In that patent, the metallic braids of a plurality of coaxial cables are terminated to a ground plate of a high speed signal transmission terminal module. The conductors/cores of the coaxial cables are terminated to signal terminals of the module.
In terminating the tubular metallic shields or braids of high speed cables to flat ground contact pads as in a printed circuit board, or to a planar ground plate as in the above-referenced U.S. patent, or to any other flat or non-tubular terminating member, various design considerations should be considered as has been found with the present invention. It should be understood that there is a transition zone created where the center conductor/core of the high speed cable goes from a xe2x80x9ccontrolled environmentxe2x80x9d wherein the conductor/core is completely surrounded by the tubular metallic shield or braid, to an xe2x80x9cuncontrolled environmentxe2x80x9d where the braid is spread away from the conductor/core for termination to the non-tubular terminating member. It is desirable that this transition zone be held to as small an area as possible and as short a length (i.e., longitudinally of the cable) as possible. Preferably, the metallic shield or braid should be terminated over an area (or at least at two points) approximately 180xc2x0 apart in relation to the center conductor/core of the cable. Preferably, the flat terminating member should overlap or at least extend to the point where the metallic shield or braid is separated from its tubular configuration surrounding the conductor/core of the cable. Still further, it is desirable that the metallic shield or braid of any given high speed cable be terminated on the same side of the flat terminating member as the center conductor/core of the cable.
The present invention is directed to solving the above-identified problems and satisfying as many of the above-identified design parameters as possible in an improved system for terminating the metallic shield of a high speed cable to a terminating member, such as a ground plate.
An object, therefore, of the invention is to provide a new and improved system or terminal for terminating the metallic shield of a high speed cable.
In the exemplary embodiment of the invention, at least one high speed cable is prepared by removing a portion of the outer jacket of the cable to expose a portion of the metallic shield of the cable. The terminal includes a conductive ground plate portion. A hump projects from one side of the ground plate portion, and the hump has a slot for receiving the cable at a location along the cable in registry with the exposed metallic shield thereof. A solder connection is provided between the metallic shield and the ground plate portion at the hump.
As disclosed herein, the terminal is stamped and formed of conductive sheet metal material, with the ground plate portion being generally planar, and with the hump being formed out of the ground plate portion. The solder connection is located substantially within the slot. Preferably, the slot has a width that is dimensioned to receive the high speed cable with a press-fit at the exposed metallic shield thereof.
The preferred embodiment of the invention includes one of the humps on each opposite side of the ground plate portion. Each of the humps includes a pair of the slots for receiving a pair of cables in a generally parallel side-by-side relationship on each opposite side of the ground plate portion. Therefore, the terminal can terminate the metallic shields of four generally parallel cables.
Other objects, features and advantages of the invention will be apparent from the following detailed description taken in connection with the accompanying drawings.